Spit-powered battery requires just a drop of saliva

In the quest to create technology that can power our lives even in the most remote of locations, we've seen some interesting ideas. Urine, tofu waste, orange peels and more have been looked to as sources of energy and now we can add spit to that list.

Researchers at Binghamton University have developed a battery that runs on a drop of saliva. The small, paper-based batteries could be used in natural disasters and remote settings where on-demand power is hard to come by. The batteries, which are more like tiny microbial fuel cells, are inexpensive to make and could serve as a power source for medical diagnostic tests in developing countries.

"On-demand micro-power generation is required especially for point-of-care diagnostic applications in developing countries," said Professor Seokheun Choi. "Typically, those applications require only several tens of microwatt-level power for several minutes, but commercial batteries or other energy harvesting technologies are too expensive and over-qualified. Also, they pose environmental pollution issues."

The bacteria-powered batteries contain freeze-dried exoelectrogenic cells which generate power when saliva is added. When just one drop is added, the paper batteries are able to produce enough power for those low-power biological sensors in just a matter of minutes.

The freeze drying allows the cells to be stored for a long time before use, which would allow them to be stocked in medical clinics around the world. The other benefit is that the biological fluid needed to activate them is readily available anywhere at any time.

Currently, the battery can only produce a few microwatts of power per square centimeter, but the researchers are working on boosting the output. The microbial fuel cells can be connected in a series to power things like LED lights, but the team is also working on making the battery more robust in order to be able to power other devices.